1. Field of the Invention
This invention relates to a copper based alloy (hereinafter referred to as "Cu alloy") which is suitable for use as a material for various electrical and electronic parts.
2. Prior Art
Conventionally, in the manufacture of various kinds of electrical and electronic parts including connectors for electrical and electronic apparatus, a Cu alloy has been used, as proposed in Japanese Provisional Patent Publication (Kokai) No. 3-56636 (hereinafter referred to as "the conventional Cu alloy"), which has a chemical composition consisting essentially, by weight percent (hereinafter referred to as "%"), of 0.5 to 3% nickel (Ni), 0.1 to 0.9% tin (Sn), 0.08 to 0.8% silicon (Si), 0.1 to 3% zinc (Zn), 0.007 to 0.25% iron (Fe), 0.001 to 0.2% phosphorus (P), and the balance of copper (Cu) and inevitable impurities.
The conventional Cu alloy possesses excellent properties required of materials for electrical and electronic parts, such as electric conductivity, high-temperature creep strength, migration resistance, plated-surface blister resistance, and solder-exfoliation resistance when bent. Therefore, the conventional Cu alloy has played an important role in realizing miniaturization and higher integration of electrical and electronic parts, as well as in enabling to withstand use under high temperature and high humidity conditions.
However, with the recent progress of mass-production of electrical and electronic parts, there has been an increasing demand for reduced manufacturing costs or reduced working costs of these parts, and accordingly there has also been an increasing demand for reduced manufacturing costs or reduced working costs of materials for these parts.
To meet these demands, attempts have been made to reduce the manufacturing cost by preparing a large-sized Cu alloy ingot to thereby decrease the number of times of preparation of the ingots, and to reduce the working cost by increasing the speed of blanking or stamping a Cu alloy sheet to thereby increase the number of electrical and electronic parts manufactured per unit time. However, those attempts have the following disadvantages:
(1) To roll the large-sized Cu alloy ingot into a plate requires an increased number of times of hot working. However, the conventional Cu alloy has insufficient hot workability such that the hot rolled ingot can have cracks formed therein after it has been subjected to a number of times of hot working. Therefore, the manufacturing cost cannot be reduced even if a large-sized Cu alloy ingot is used.
(2) Moreover, Cu alloy sheets prepared from the conventional Cu alloy have poor blankability such that high-speed blanking of the Cu alloy sheet in manufacturing electrical and electronic parts causes heavy wear of the blanking die, requiring severe maintenance of the blanking die and an increased number of times of replacement thereof with a new one. Therefore, no reduction of the working cost can be achieved.